This invention relates to adjustable chairs and in particular such chairs having both an adjustable backrest and an adjustable seat.
Adjustable chairs are well known in the furniture industry including chairs wherein both the backrest position and the seat position can be adjusted or moved to make the chair more comfortable for the user. It is also known to provide chairs in which the seat and the backrest move synchronously by way of various synchronizing mechanisms. The synchronizing mechanism is able to change the position of the seat at the same time as the backrest is adjusted.
For example, U.S. Pat. No. 5,810,440 which issued on Sep. 22, 1998 to the present applicant describes a chair having a base, a seat, a backrest, a back support and a mechanism which interconnects the seat, back and back support and imparts a predetermined synchronous movement to the seat and back, e.g. rearward tilting of the seat and simultaneous rearward tilting of the back. The chair back has a rotation mechanism for rotatably connecting the chair back to the back support. The rotation is about a rotation axis which passes through the upper body of a person when the person is sitting on the seat and resting against the chair back. The bottom portion of the chair back is guided so that the bottom can move along an arc between a first position and a second position which is forward and lower than the first position.
More recent U.S. Pat. No. 6,709,057 to Armin Sander describes an adjustable chair having a backrest that is inclinable with regards to a seat carrier via a backrest carrier. The seat surface can be moved synchronously with the backrest and is supported on the seat carrier via at least one seat link. A coupling link linking the seat and the backrest carrier is provided for synchronization between the movement of the backrest and that of the seat surface.
Despite the adjustable chairs that are known in the seating industry, there is still a need for an improved chair that can be easily manufactured while at the same time being quite sturdy and durable. There is provided herein an adjustable chair wherein the pivoting movement of the backrest for the chair differs from the amount of pivoting of the seat. In a particular exemplary embodiment of the chair, the overall tilting mechanism for the backrest and the seat causes the rear end of the seat to move backwards and downwards with respect to the backrest when the seat and backrest are tilted backwardly and simultaneously the bottom edge of the backrest to move downwards and slightly rearwards with respect to the rear edge of the seat, thus reducing the horizontal and vertical gap between the rear end of the seat and the backrest.